can ne 1 tell me how mixing valves un-adjust?

Advertisement

can ne 1 tell me how mixing valves un-adjust?

I only have the info, i did not recieve any pics, but it is at a grocerie store, and we ran out of hot water to the sinks. The plumbing tech said he diagnosed everything and found the problem to be coming from the Mixing Valves, he said all he did was "adjust the mixing valves". That costed me alot of $ and so I was just curious as to how they became un-adjusted? Do they just do that by themselves?